Electric drive units consist of a stator and a rotor that is moved in relation to the stator. In such motors, electrical power on the rotor is sometimes required, for example:                to control the drive power by having a separate supply for the rotor, such as, for example, exciter power in an electrically excited synchronous motor or dual fed asynchronous motor.        as auxiliary energy for loading and unloading in transport tasks, clamping of work pieces or tools, for sensor systems to detect temperature and position, for example, and for data transmission systems.        
Energy transmission in a drive unit requires a suitable energy transmission system. Since the drive unit is designed, depending on the application, as a synchronous motor, an asynchronous motor or a reluctance motor, including specific sub-types, a number of parameters need to be considered in the design thereof. The energy transmission system has to be integrated into the working unit or attached separately. In the prior art, the power required is transmitted for example, by means of sliding contacts or trailing cables (where the path and angle for maneuver is restricted). The provision of a separate energy transmission system with a spatially separate active part is also known; in for example, the exciter in a synchronous motor, or linear inductive energy transmission systems. This principle is described in DE 42 36 340 A1, for example.
Problems inherent these known solutions to the problem are:                additional space/weight required for the energy transmission system: in the case of trailing cables, the weight of trailing cables moved is even variable.        wear, friction, contamination.        
A procedure known from DE 10 2005 024 203 A1 consists of accommodating the drive function and energy transmission function in a common active part and ensuring by appropriate selection of the winding parameters that the drive function and the energy transmission function can to a large extent be operated independently.